CN101377413A - Method for measuring photoresist mask slot-shaped structure parameter - Google Patents

Abstract

The invention discloses a method for measuring photoresist mask groove shape structure parameter, which is characterized in that TE/TM linearly polarized light which is used as incident light and the blaze angle of the measured mask which is used as incident angle are utilized to measure the spectral distribution D0 (Lambada) of the reflected light of a standard reflected slice and the spectral distribution D (Lambada) of the reflected and diffracted zero level polychromatic light of the measured mask. A comparison method is utilized to calculate actual reflected and diffracted zero level spectral distribution Rg (Lambada) of a dielectric layer raster mask. The actual reflected and diffracted zero level spectral distribution Rg (Lambada) is processed by spectrum inversion to get the groove parameter of the mask, such as the residual thickness of the photoresist, groove depth and duty cycle and so on. The method realizes the undamaged detection to the groove parameter of large area and great weight of masks, can avoid the error of the measuring system, has no special requirement to spectrograph measuring system and light source, and has simple and easy measuring method.

Description

A kind of method of measuring the photoresist mask slot-shaped structure parameter

Technical field

The present invention relates to a kind of minute sized non-destructive measuring method, be specifically related to a kind of method that is used to measure the slot-shaped structure parameter of photoresist mask.

Background technology

The ion etching deielectric-coating grating (to call pulse compression grating in the following text) that is used for the laser pulse compression is the key element that obtains ultrashort superhigh intensity laser, and multilayer dielectric film substrate photoresist grating is as the mask of making pulse compression grating, and its quality is directly connected to the quality of pulse compression grating.The detection of multilayer dielectric film substrate photoresist grating mask (to call the deielectric-coating grating mask in the following text) quality is an important quality control link in the pulse compression grating through engineering approaches manufacturing process.

The deielectric-coating grating mask is a kind ofly to be coated with on the optical base-substrate of deielectric-coating the grating of making of photo anti-corrosion agent material, be used for the transfer of ion etching technology optical grating construction, similar with the mask that is used for figure transfer in the semiconductor technology, its bathtub construction as shown in Figure 1.The quality of deielectric-coating grating mask is by its flute profile parameter characterization, that is: the residual thickness of photoresist, groove depth and account for wide ratio wherein account for wide ratio and be defined as the grating tooth in the width of Ban Yaochu and the ratio in grating cycle (it be actually obtain by measurement of length).The yardstick of deielectric-coating grating mask flute profile parameter, detects the surface microscopic topographic of this yardstick to micron dimension in sub-micron, and the means that adopt are scanning electron microscope (SEM), atomic force microscope (AFM) or atomic force contourgraph (AFP) usually.Detect with scanning electron microscope, sample need be blocked, under electron microscope, obtain the information of surface microscopic topographic vertical and horizontal, thus, certainly will cause expendable destruction sample by the situation of measuring section.In the semi-conductor chip manufacturing, often will (periodic micro structure that is generally 100um * 100um) can't harm online detection to some small sizes, what adopt usually is AFM or AFP measurement means, AFM, AFP will not block with regard to the information of energy measurement to the surface microscopic topographic vertical and horizontal by sample, but only are applicable to the sample that detects small area usually.Existing commercial AFM, AFP are inapplicable for the large tracts of land sample.

The deielectric-coating grating mask is different with semi-conductor chip, it has the characteristics of area big (normally hundreds if not thousands of square centimeters), Heavy Weight (several kilograms or tens of kilogram), these characteristics make survey instruments such as present SEM, AFM, AFP not have possibility substantially when detecting its pattern parameter.Therefore, development is very necessary to large tracts of land deielectric-coating grating mask flute profile parameter detection method that can't harm, effective, practical.

Summary of the invention

The object of the invention provides a kind of method that is used for the slot-shaped structure parameter of photoresist mask is carried out Non-Destructive Testing, is applicable to the determining of structural parameters of large-area deielectric-coating grating mask flute profile.

For achieving the above object, the technical solution used in the present invention is: a kind of method of measuring the photoresist mask slot-shaped structure parameter, and adopting the TE/TM linearly polarized light is incident light, incident angle is the blazing angle (Littorw angle) of tested mask, comprises the steps:

(1) the standard reflection sheet is placed on the specimen holder, and with the reflected light of standard reflection sheet with the entrance slit of lens focus to spectrometer, measure this catoptrical spectral distribution D ₀(λ);

(2) tested mask is placed on the specimen holder, the reflection diffraction zero level polychromatic light of tested mask is focused to the entrance slit of spectrometer, measure the spectral distribution D (λ) of this reflection diffraction zero order light;

(3) according to following formula,

D(λ)＝I ₀(λ)·R _g(λ)·T(λ)

D ₀(λ)＝I ₀(λ)·R ₀(λ)·T(λ)

In the formula, I ₀Be the radiation power distribution of incident ray polarized light (λ), T (λ) is the spectral transfer function of spectral measurement system, R ₀(λ) be the reflectivity of standard reflection sheet;

Adopt relative method, calculate the spectral distribution R of the reflection diffraction zero level of deielectric-coating grating mask reality _g(λ), it is carried out the spectrum inverting, obtain the flute profile parameter of mask: the residual thickness of photoresist, groove depth and account for wide ratio.

The main thought of technique scheme is, the spectral distribution of the reflection diffraction zero level by measuring media film grating mask goes out the flute profile parameter of deielectric-coating grating mask then according to this distribution inversion.This detection method except being used for determining the flute profile parameter of deielectric-coating grating mask, can also be used for the flute profile parameter of the known grating/grating mask of definite substrate reflection coefficient.

After the light of different wave length was incident to grating generation diffraction, the diffraction efficiency of grating of the same order of diffraction time different wavelengths of light was different, and we call the inferior diffraction efficiency of grating down of same stages the spectral distribution of certain order of diffraction of grating with wavelength change.Theoretical research shows that under the certain prerequisite of incident condition, the grating diffration efficiency eta depends on the flute profile parameter of grating.

${\mathrm{\η}}_n^{\left(1\right)}=\frac{{\mathrm{\β}}_n^{\left(1\right)}}{{\mathrm{\β}}_0^{\left(1\right)}}{\left|A_n^{\left(1\right)}\right|}^2---\left(1\right)$

${\mathrm{\η}}_k^{\left(2\right)}=\frac{{{\mathrm{\ϵ}}_2\mathrm{\β}}_k^{\left(2\right)}}{{{\mathrm{\ϵ}}_1\mathrm{\β}}_0^{\left(1\right)}}{\left|A_k^{\left(2\right)}\right|}^2---\left(2\right)$

Wherein subscript (1), (2) are represented reflection diffraction and transmission diffraction respectively, and n, k represent the level of diffraction inferior,

With Relevant with the wave vector of incident, reflection diffraction and transmission diffraction ripple respectively, for:

${\mathrm{\&beta;}}_n^{\left(1\right)}={({\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="A200810156859E00101.png"\; state="\{\{state\}\}">n</figure-callout>}}_1^2{k}_0^2-{\mathrm{\&alpha;}}_n^2)}^{1/2}$

${\mathrm{\&beta;}}_k^{\left(2\right)}={(n_2^2{k}_0^2-{\mathrm{\&alpha;}}_k^2)}^{1/2}$

α _m＝n ₁k ₀sinθ+mK， m＝n，k $K=\frac{2\mathrm{\&pi;}}{d}$

$k_0(=\frac{2\mathrm{\&pi;}}{{\mathrm{\&lambda;}}_0})$ Be incident light wave number in a vacuum, θ is an incident angle, n ₁, n ₂Be respectively the refractive index of incident light place medium and photoresist.

With

Expression reflection and transmission diffraction wave amplitude, (Δ, h, tr) is relevant with incident condition, grating flute profile parameter for they.Do not have simple analytic relationship formula between amplitude and the flute profile parameter, we are shown by simple table:

$A_n^{\left(1\right)}=f_n^{\left(1\right)}(\mathrm{\&Delta;},h,\mathrm{tr})$

$A_k^{\left(2\right)}={f_k}^{\left(2\right)}(\mathrm{\&Delta;},h,\mathrm{tr})$

Then grating diffraction efficiency at different levels is expressed as:

${\mathrm{\&eta;}}_n^{\left(1\right)}=\frac{{\mathrm{\&beta;}}_n^{\left(1\right)}}{{\mathrm{\&beta;}}_0^{\left(1\right)}}{\left|{f_n}^{\left(1\right)}(\mathrm{\&Delta;},h,\mathrm{tr})\right|}^2$

${\mathrm{\&eta;}}_k^{\left(2\right)}=\frac{{\mathrm{\&beta;}}_n^{\left(2\right)}}{{\mathrm{\&beta;}}_0^{\left(1\right)}}{\left|{f_k}^{\left(2\right)}(\mathrm{\&Delta;},h,\mathrm{tr})\right|}^2$

Writing computer program by Maxwell equation and corresponding boundary condition can be in the hope of the numerical solution of the diffraction efficiency at different levels of grating under certain incident condition and the flute profile parameter; Conversely, if known grating diffration efficient can also obtain the information of flute profile parameter.When polychromatic light was incident to grating, the spectral distribution of the diffraction efficiency that grating is at different levels then can be expressed as:

${\mathrm{\&eta;}}_n^{\left(1\right)}\left(\mathrm{\&lambda;}\right)=\frac{{\mathrm{\&beta;}}_n^{\left(1\right)}}{{\mathrm{\&beta;}}_0^{\left(1\right)}}{\left|{f_n}^{\left(1\right)}(\mathrm{\&Delta;},h,\mathrm{tr},\mathrm{\&lambda;})\right|}^2$

${\mathrm{\&eta;}}_k^{\left(2\right)}\left(\mathrm{\&lambda;}\right)=\frac{{\mathrm{\&beta;}}_n^{\left(2\right)}}{{\mathrm{\&beta;}}_0^{\left(1\right)}}{\left|{f_k}^{\left(2\right)}(\mathrm{\&Delta;},h,\mathrm{tr},\mathrm{\&lambda;})\right|}^2$

By following formula as seen, under certain incident condition, the spectral distribution of grating diffraction efficiencies at different levels is by flute profile parameter (Δ, h, the tr) decision of grating, and there is corresponding relation mutually in the spectral distribution of optical grating diffraction level with the flute profile parameter of mask in theory.

Therefore, if the spectral distribution η of diffraction efficiency of grating (λ) is known, can obtain the numerical solution of the flute profile parameter (Δ, h, tr) of grating by computing machine.

If the radiation power of incident ray polarized light is distributed as I ₀(λ), under the incident of Littrow angle, the spectral distribution of the reflection diffraction zero level of deielectric-coating grating mask is R _g(λ), the spectral transfer function of spectral measurement system is T (λ), and the light distribution that spectrometer measurement obtains is D (λ):

D(λ)＝I ₀(λ)·R _g(λ)·T(λ) (3)

For the spectral distribution information of the reflection diffraction zero level that obtains the deielectric-coating grating mask, (its reflectivity is R to adopt a standard reflecting plate ₀(λ)), under same incident angle,, be D with its catoptrical spectral distribution of same spectrometer measurement ₀(λ):

D ₀(λ)＝I ₀(λ)·R ₀(λ)·T(λ) (4)

(1), (2) two formulas are compared and can be got:

$R_g\left(\mathrm{\&lambda;}\right)=\frac{D\left(\mathrm{\&lambda;}\right)}{D_0\left(\mathrm{\&lambda;}\right)}\&CenterDot;R_0\left(\mathrm{\&lambda;}\right)---\left(5\right)$

Obtain the spectral distribution R of deielectric-coating grating mask reflection diffraction zero level _g(λ), obtain the flute profile parameter of deielectric-coating grating mask by the spectrum inverting.

As seen from the above, owing to adopted comparative measurement method, this method can be avoided the error of measuring system, and spectrometer measurement system and light source are not had special requirement, and measuring method is simple.

Wherein, the inversion method of flute profile parameter:

Deielectric-coating grating mask with unknown flute profile parameter is a research object, make up suitable objective optimization function, utilization direct search algorithm, correlativity between the corresponding a series of diffraction zero-level spectral distribution curve of the diffraction zero-level spectral distribution curve (aim curve) of the research object that judgment experiment measures and various flute profile parameter, thus the optimal slot shape parameter of mask obtained.

The objective optimization function that makes up in the direct search algorithm is:

$\min :F(h,\mathrm{tr},\mathrm{\&Delta;})=1-R(h,\mathrm{tr},\mathrm{\&Delta;})\&CircleTimes;R_g\left(\mathrm{\&lambda;}\right)---\left(6\right)$

R wherein _gBe the spectral distribution curve of flute profile parameter deielectric-coating grating mask diffraction zero-level light undetermined (λ), it is obtained by experiment measuring; R (h, tr, Δ) is the various possible flute profile parameter values spectral distribution curves of corresponding a series of diffraction zero-level light down, two curves are done correlation computations, pairing h when the two related coefficient maximum (that is objective optimization function F (h, tr, Δ) is a minimum value), tr, the value of Δ promptly is the flute profile parameter that the spectrum method of inversion obtains.The related coefficient value is big more, and the numerical value of the flute profile parameter that inverting obtains is accurate more, and correspondingly inverting is also long more required computing time.

Because the technique scheme utilization, the present invention compared with prior art has following advantage:

1. the present invention creatively distributes by the reflection diffraction zero order spectrum of measuring mask to be measured, and spectrum is carried out inverting, obtains the flute profile parameter of mask, has realized the Non-Destructive Testing for the flute profile parameter of all bigger mask to be measured of area, weight;

2. the present invention has adopted comparative measurement method when the reflection diffraction zero order spectrum of measuring mask to be measured distributes, and this method can be avoided the error of measuring system, and spectrometer measurement system and light source are not had special requirement, and measuring method is simple.

Description of drawings

Fig. 1 is a grating mask bathtub construction synoptic diagram;

Fig. 2 is the measuring method schematic flow sheet of the embodiment of the invention one;

Fig. 3 is the measurement light path synoptic diagram of embodiment one;

Fig. 4 is a curve of spectrum match condition synoptic diagram among the embodiment one.

Embodiment

Below in conjunction with drawings and Examples the present invention is further described:

Embodiment one: referring to accompanying drawing 1 to shown in the accompanying drawing 4, a kind of method of measuring the photoresist mask slot-shaped structure parameter, it is as follows to measure detailed process:

(1) measure light path according to foundation shown in Figure 3, regulate the polarizer, making the incident secondary color directional light that is incident on the tested mask is the TE/TM linearly polarized light;

(2) regulate the specimen holder angle, making incident angle is the Littrow angle (being the θ angle) of tested grating, the fixed sample frame;

(3) earlier the standard reflection sheet is placed on the specimen holder, with lens the reflected light of standard reflection sheet is focused to the entrance slit of spectrometer, with the catoptrical spectrum D of spectrometer measurement standard reflector plate ₀(λ);

(4) finish the measurement of standard reflection sheet reflectance spectrum after, with standard reflection sheet under the mask displacement, with lens the reflection diffraction zero level polychromatic light of mask is focused to the entrance slit of spectrometer, with the spectral distribution D (λ) of the reflection diffraction zero order light of spectrometer measurement mask;

(5) according to formula (3), (4), (5), utilize relative method, obtain the spectral distribution curve R of the reflection diffraction zero level of deielectric-coating grating mask reality _g(λ);

(6) by formula the objective optimization function in (6) structure direct search algorithm, set the hunting zone of mask flute profile Rational Parameters, correlation theory (seeing theoretical analysis related in the summary of the invention) according to the Maxwell electromagnetic field, calculate the spectral distribution curve R (h of all diffraction zero-level light of various flute profile parameter value correspondences in the hunting zone, tr, Δ);

(7) finish all R (h, tr, Δ) curve and R _g(λ) related operation of curve calculates related coefficient, as certain bar spectral distribution curve and experiment measuring curve R _gWhen related coefficient (λ) is maximum (objective optimization function F (h, tr, Δ) minimum value), the spectrum inverting finishes, the pairing h of curve R (h, tr, Δ) this moment, and tr, the value of Δ promptly is the flute profile parameter that the spectrum method of inversion obtains.

Below be the theoretical validation result that the spectrum method of inversion is determined mask flute profile parameter.Spectral distribution curve with the reflection diffraction zero level of the grating mask (its flute profile parameter is the desired value in the table 1) of particular medium film substrate is aim curve R _g(λ), according to above-mentioned steps (6), (7) institute those set forth, it is implemented the spectrum inverting, spectral range gets that 400nm～700nm, spectral resolution get 5nm, polarization mode is TE, is finally inversed by the flute profile parameter (i.e. optimal value in the table 1) of this grating mask.The relevant matches situation of the pairing curve of spectrum of flute profile parameter values (aim curve) and the pairing curve of spectrum of inversion result (inversional curve) as shown in Figure 4.

Table 1 mask flute profile parameter spectrum inversion result

Claims (1)

1. method of measuring the photoresist mask slot-shaped structure parameter is characterized in that: adopting the TE/TM linearly polarized light is incident light, and incident angle is the blazing angle of tested mask, comprises the steps:

(1) the standard reflection sheet is placed on the specimen holder, and with the reflected light of standard reflection sheet with the entrance slit of lens focus to spectrometer, measure this catoptrical spectral distribution D ₀(λ);

(2) tested mask is placed on the specimen holder, the reflection diffraction zero level polychromatic light of tested mask is focused to the entrance slit of spectrometer, measure the spectral distribution D (λ) of this reflection diffraction zero order light;

(3) according to following formula,

D(λ)＝I ₀(λ)·R _g(λ)·T(λ)

D ₀(λ)＝I ₀(λ)·R ₀(λ)·T(λ)

In the formula, I ₀Be the radiation power distribution of incident ray polarized light (λ), T (λ) is the spectral transfer function of spectral measurement system, R ₀(λ) be the reflectivity of standard reflection sheet;

Adopt relative method, calculate the spectral distribution R of the reflection diffraction zero level of deielectric-coating grating mask reality _g(λ), it is carried out the spectrum inverting, obtain the flute profile parameter of mask: the residual thickness of photoresist, groove depth and account for wide ratio.

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